The present invention is directed to a data cartridge library and, in particular, to an architecture for a data cartridge library that yields a high data density footprint.
Data cartridge library systems are primarily used to archive data, i.e., store data that is or may be important to the user of a computer system or network but not immediately needed by the user. To elaborate, the typical library system receives data from a host computer and stores the data in one or more data cartridges. When the host computer requires some of the data that was previously stored in a data cartridge, a request for the data is sent from the host computer to the library system. In response, the library system locates the data cartridge in which the desired data is located, retrieves the data from the recording medium within the cartridge using a drive, and transmits the data to the host computer system.
The typical data cartridge library system is comprised of: (a) a plurality of storage slots, with each slot capable of holding a data cartridge; (b) one or more drives, with each drive at least capable of reading data that has been stored in a data cartridge and, more typically, capable of reading data stored in a data cartridge and writing data on the recording medium located within a data cartridge; (c) a transport device that is capable of moving data cartridges between the slots and the drive(s); and (d) an interface for transferring data between the library system and a host computer, where the transfer typically takes place over a computer network that includes two or more host computer systems. The operation of reading data previously stored in a data cartridge located in the library begins with the transport device locating the slot that holds the cartridge with the desired data, removing the cartridge from the slot, transporting the cartridge to the drive, and facilitating the insertion of the cartridge into the drive. The drive then reads the desired data from the recording medium located in the cartridge and provides the data to the interface for transport to the host computer that requested the data. After the desired data has been read, the transport mechanism facilitates the removal of the cartridge from the drive, transports the cartridge to a slot (typically, the slot from which the cartridge was originally retrieved), and inserts the cartridge into the slot. The operation of writing data on the recording medium located in a cartridge involves the use of the transport mechanism to move a cartridge from a slot to a drive. After the cartridge is installed in the drive, data from a host computer that has been received at the interface is written or established on the recording medium within the cartridge by the drive. After the data has been written on the recording medium, the transport mechanism retrieves the cartridge from the drive and transports the cartridge to a slot for storage.
The present invention is directed to a data cartridge library architecture that provides a high data density footprint, i.e., the amount of data that the library architecture is capable of storing when the maximum number of data cartridges are housed within the library divided by the floor space occupied by the library is relatively high. A high data density footprint is important in applications where the floor space that can be dedicated to data storage is limited and the amount of data that needs to be stored is relatively large. One notable example of such an application is data centers that provide off-site xe2x80x9cbackupxe2x80x9d or xe2x80x9cmirroringxe2x80x9d of the data stored on their clients computer systems. Such data centers want to maximize the amount of data that can be stored in a given floor space.
In one embodiment, a data cartridge library system is provided that comprises a cabinet with side walls that define a rectangular, box-like structure which defines an interior space. Located within the interior space are one or more drives, with each drive capable of at least reading data that has been previously established on the recording medium within a data cartridge. Also situated within the interior space is a shelf system that is capable of supporting at least two data cartridge drawers. The shelf system includes at least one shelf that extends outwards from one of two, opposite walls of the cabinet but terminates before reaching the other of the two, opposite walls, i.e., terminates within the interior space. A transport mechanism is substantially free to move within a space that extends between the end of a drawer located on the shelf and the other of the two, opposite walls of the cabinet. Stated differently, the space between the two opposite walls includes: (1) a first space between one of the two, opposite walls and the end of a drawer located on the shelf that is dedicated to supporting the drawer, and (2) a second space between the end of the drawer that faces the interior space when the drawer is on the shelf and the opposite wall that is dedicated to a transport mechanism, i.e., the transport mechanism is free to move in this space. The drawers each include a plurality of slots, with each slot capable of holding a data cartridge in an orientation such that the face of the cartridge with the greatest surface area is substantially parallel to the two, opposite sides of the cabinet between which the shelf extends or substantially parallel to the other two, opposite sides of the cabinet. Additionally, the shelf is situated such that when a drawer is on the shelf, at least one of the slots cannot be accessed for either removal/insertion of cartridges. As a consequence, the drawer must be withdrawn from the shelf and into the space dedicated to the transport mechanism so that the slot or slots not otherwise accessible for removal/insertion of data cartridges are accessible.
In one embodiment, the shelf system includes two shelves, the first shelf extending from the first side of the cabinet and the second shelf extending from the opposite side of the cabinet. The two shelves are substantially at the same height or elevation in the cabinet. With the two shelves oriented in this fashion, it is possible to move a drawer from the first shelf to the second shelf with a transport mechanism and without repositioning the transport mechanism. In this embodiment, it should be appreciated that the space within which the transport mechanism is able to freely move is located between the two shelves.
In another embodiment, a shelf within the shelf system includes a first orientation structure for cooperating with a second orientation structure on a drawer to insure that when a drawer is situated on the shelf, the drawer is oriented such that one end of the drawer is located adjacent to the side of the cabinet. The ability to orient the drawer in this manner facilitates the orientation of any data cartridges located in the drawer for grasping by a transport mechanism. To elaborate, the drawer employs additional orientation structures, one associated with each slot, to insure that any data cartridges in the drawer each have the same an orientation within the drawer. The first and second orientation structures and the orientation structures within the drawer insure that any data cartridges located within the drawer present the same orientation to the transport mechanism. This, in turn, facilitates the grasping of the data cartridges by the transport mechanism.
In yet another embodiment, when the shelf system includes shelves extending from opposite sides of the cabinet, the orientation structure associated with the first shelf that extends from the first side is the mirror image of the orientation structure associated with the second shelf that extends from the opposite side. Consequently, these orientation structures avoid any need, in transferring of a drawer from the first shelf to the second shelf, to rotate the drawer about a vertical axis.
In another embodiment, the shelf includes a first retaining structure that cooperates with a second retaining structure on a drawer to hold the drawer on the shelf. In one embodiment, the first retaining structure and second retaining structure form a passive latch that is actuated as a result of the transport mechanism withdrawing the drawer from the shelf or pushing the drawer onto the shelf. In other embodiments, an active latch is employed that is again comprised of a first retaining structure associated with the shelf and a second retaining structure associated with the drawer. However, in the case of an active latch, the transport mechanism is required to actuate the latch so that a drawer can be withdrawn from the shelf.
Other embodiments employ a shelf system with multiple shelves in various configurations. Possible multiple shelf configurations include: (1) at least two shelves, each extending from the first side of the cabinet and with one shelf located at a higher elevation than the other shelf; (2) at least three shelves, with two shelves extending from the first side with one shelf at a higher elevation than the other shelf and the third shelf extending from the opposite side of the cabinet; and (3) at least four shelves, with two shelves extending from the first side with one shelf at a higher elevation than the other shelf and with the other two shelves extending from the opposite side with one shelf at a higher elevation than the other shelf.
Yet a further embodiment employs a drive oriented such that the face of the drive that has the opening for receiving a data cartridge is substantially parallel to the side of the cabinet from which a shelf extends. Another embodiment utilizes a drive that is oriented such that the face of the drive that has the opening for receiving a data cartridge is substantially parallel to a side of the cabinet from which a shelf does not extend. Stated differently, the drive is located between the two opposite sides between which one or more shelves extend.